Fractal Analysis of Polymeric and Particulate Titania Aerogels by Adsorption

Abstract

Polymeric and particulate titania (TiO 2 ) aerogels with high surface areas were prepared from sol−gel derived TiO 2 lyogels via freeze-drying as well as CO 2 supercritical drying. The surface fractal dimensions of these aerogels were evaluated with two methods based on physisorption, one by Avnir and Pfeifer, and the other, the modified form of the Frenkel−Halsey−Hill (FHH) equation. The two approaches yielded almost identical results. The surface fractal dimensions measured are approximately 2.7 and 2.8 for polymeric and particulate TiO 2 aerogels, respectively, thereby indicating that the fractal surfaces of particulate aerogels are slightly more irregular than those of polymeric aerogels.